Perry, who also sought the GOP nomination before dropping out in September, said he now sees the race as one that is between Cruz, a fellow Texan, and Donald Trump. Through phone calls and during a December day spent driving around his Round Top, Texas, home in his truck with Cruz, Perry said he found the senator to be a good listener who respects the Tenth Amendment, “knows what he does not know” and is more conservative than Trump.

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“Of those individuals who have a chance to win the Republican primary, at this juncture, from my perspective, Ted Cruz is by far the most consistent conservative in that crowd,” Perry said. “And that appears to be down to two people."

Perry, who is famously skilled at retail politics, will campaign with Cruz Tuesday across Iowa, and will join Iowa GOP Rep. Steve King to stump for Cruz again Wednesday. Perry and King will both join Cruz at a Des Moines rally Wednesday night.

The endorsement gives Cruz the blessing of the longest-serving governor in Texas history, just as the senator faces intensifying heat from other veteran politicians, including from his colleagues in Washington, Iowa Gov. Terry Branstad and former Senate Majority Leader Bob Dole.

Perry, recalling his own experience vetoing a long list of bills early in his gubernatorial tenure, said his actions resulted in others viewing him as a “man of principle,” and insisted that Cruz would similarly be able to get things done as president, despite his current reputation among fellow senators for being a bomb-thrower.

“You’ll have with Ted Cruz that same result of, senators and others in the Washington establishment that are mad at him, find him to be hard to work with, they will find a way to work with him because they know he means what he says he means,” he said.

Perry has been dismissive in the past of the experience of first-term senators compared to governors. But he said Sunday that he has come to realize the GOP electorate doesn’t value executive experience this cycle in the same way he does.

“Gov. Scott Walker, Bobby Jindal, Rick Perry, Jeb’s barely making an impact out there — those are very skilled, very successful, very experienced governors,” Perry said. “But the electorate doesn’t want that. That’s why we have elections, why we democratically select leaders.”

And he is confident, he said, that Cruz would be prepared.

“He knows he’s going to surround himself with people who do have that experience, and I’m very satisfied that on Day 1, he will be ready to be commander-in-chief,” Perry said, “Partly because of the time he’s going to spend in learning what he doesn’t know, but he’s also surrounding himself with people who are extraordinarily capable and wise.”

Perry’s endorsement was hardly a sure bet. The two were on opposite sides of the 2012 Senate primary race, when Cruz ran successfully against Perry’s then-lieutenant governor, David Dewhurst, in a contest that launched Cruz on the national stage. In his farewell address before the Republican-dominated state legislature last year, Perry warned against those who would place “purity ahead of unity” — a frequent criticism of Cruz's style. And Perry was somewhat critical of Cruz’s role in shutting down the government in 2013 over a health care battle.

“I’d rather see folks come together, work together to find solutions, but from time to time, you’ve got to lay the marker down,” Perry said, when asked whether Cruz could work with Washington. “There’s that old adage, ‘You gotta hit the mule upside the head to get its attention from time to time.’ I’d suggest that’s exactly what the senator was doing.”

Perry, an Air Force veteran and champion of veterans’ issues, is expected to be particularly helpful in courting veterans, especially in South Carolina, which is home to prominent military bases and an electorate with a strongly pro-military bent — and where Perry had a well-respected team.

Shortly before he exited the race in the fall, Perry had emerged as one of the field’s most pointed critics of Trump, a mantle Cruz now holds as he and Trump battle for first place in Iowa. The former Texas governor noted that a number of other prominent conservatives, including media personality Glenn Beck, have come out against Donald Trump, something Trump’s “going to have to explain.”

After Perry dropped out of the primary, Cruz's campaign immediately began courting his donors and supporters in Texas, while Cruz reached out to the former governor and asked to get together -- a gesture Perry says he appreciated given how little down time candidates get off the trail. When they met, Perry said, Cruz struck him as someone who deep down is likely “shy,” and “one of the best listeners I’ve ever dealt with in the political realm.” It was in stark contrast to more negative perceptions he had held about Cruz, driven by "media narrative" and "through the optics of a campaign."

“I really didn’t want to talk about policy, I didn’t want to talk politics, I didn’t want to talk philosophy,” he said of their meeting last month. “I wanted to talk about him, who he was, see if I could get a handle on Ted Cruz the man, not Cruz the caricature I’d seen through the political lens. What I found was a very different person than what I had been led to believe.”